1. Field of the Invention
This invention relates to assistive aids for the physically challenged. More specifically, it relates to aids for sensing gross body motions such as nods of the head or motions of a limb, for the purpose of signaling other assistive appliances such as computer speech software.
2. Description of Prior Art
Several medical disorders including cerebral palsy cause loss of muscle control, and in severe cases speech loss, making it difficult or nearly impossible for some people to communicate. One useful aid is E Z Keys from Words+Inc., which allow one to form words and sentences by making selections from menus. Such selections may be made by the user closing a switch, as for example by a movement of their head. For example, such a switch might be placed above and behind a head rest, where it can be reached by a user if they arch their head upwards and backwards. Such switches are available from AbleNet Inc. Another switch, the xe2x80x9cPetite Pillow Switch from Toys for Special Children Inc. uses a balloon-bladder to sense when a person reaches out and presses on it. Other similar concepts are disclosed in the xe2x80x9cEducational Organizerxe2x80x9d of U.S. Pat. No. 5,601,432.
Unfortunately, none of these switches can support static loads, such as a person""s head or limb, because they would always be switched on. Often, for them to work at all, they must be used together with a supplemental support such as a head rest. The problem then becomes aligning the switch to the support, which is seldom long-lasting, because individuals who require such devices will likely not have sufficient muscle control to maintain a particular posture. The problem is compounded by the user likely not being able to communicate which adjustments are best, with the result usually being a poor compromise. Further, the alignment is often so complicated as to be beyond the skills of alternative care-givers, and merely changing a seating angle can ruin an otherwise good alignment. For many users, these switches are a constant source of frustration and aggravation.
What is needed is a comfortable assistive switch that is easy to set up, and is self-accommodating of a user""s changing posture.
The present invention is an improved and self-adjusting sensing and signaling device for the disabled. The device senses human contact bumps, and beneficially is not affected by static loads or shifting postures.
The apparatus may be characterized as a being a pneumatic system. It""s first key component is a small cushion, which importantly is self-inflating. This is accomplished preferably by its being filled with an elastomeric foam. When a user desires to send a signal, and bumps or otherwise presses anywhere on the cushion, the air pressure in the cushion momentarily increases slightly, typically less than one percent.
This brief pressure increase is detected by a second key component, a sensitive air pressure sensor. This sensor in its simplest form is a pressure switch, whose electrical contacts can be used to signal a computer or other electronic device.
An important third component of the pneumatic apparatus is an air bleed, which slowly over many seconds equalizes the pressure inside and outside the system. The function of the bleed is to allow the apparatus to be self-adjusting. By equalizing the gauge pressure inside and outside the system, the switch will not close under the weight of static loads such as body weight. Instead, the weight of the load is supported by the comfortable elastomeric form inside the cushion. Thus the apparatus is able to also act as a body support, without generating continuous signals.
By providing service as both a body support and a signaling device, the apparatus overcomes the limitation of previous devices, that of requiring complicated and impermanent alignments. In the present apparatus, such alignment is automatic and long-lasting, and also accommodating of shifts in a user""s body posture. Its soft cushion is more comfortable than a hard switch. Users become able to send signals many times more rapidly and many times more controllably, even after hours and hours of extended use.